1. Field of the Invention
The present invention relates to the field of display, and in particular to a driving method for in-cell type touch display panel.
2. The Related Arts
The gate driver on array (GOA) technology is the array substrate column drive technology, by using the thin film transistor (TFT) liquid crystal display (LCD) array processor to manufacture the gate scan driver circuit on the TFT array substrate to realize the column-by-column scan driving. The GOA technology has the advantages of low manufacture cost and the ability to realize narrow-border panels, and is used by many types of displays. GOA circuit has two basic functions: first, to output scan driving signal to drive the gate line in the panel to turn on the TFT in the display area so as to charge the pixels; and the second is the shift register; when the N-th scan driving signal is outputted, the clock control is used to perform outputting the (N+1)-th scan driving signal, and so on.
With the development of the low temperature poly-silicon (LTPS) semiconductor TFT, LTPS TFT liquid crystal display (LCD) attracts much attention. Because LTPS silicon crystal is more orderly arranged than non-crystal silicon, LTPS semiconductor shows a ultra-high carrier migration rate. The LCD utilizing LTPS TFT has the advantages of high resolution, rapid response, high luminance, and high opening ratio. Correspondingly, the integrated circuit (IC) around the panel of LTPS TFT LCD also becomes a focus of the display technology. The gate driver on array (GOA) technology is the array substrate column drive technology, by using the thin film transistor (TFT) liquid crystal display (LCD) array processor to manufacture the gate scan driver circuit on the TFT array substrate to realize the column-by-column scan driving. The GOA technology has the advantages of low manufacture cost and the ability to realize narrow-border panels, and is used by many types of displays. GOA circuit has two basic functions: first, to output scan driving signal to drive the gate line in the panel to turn on the TFT in the display area so as to charge the pixels; and the second is the shift bit saving; when the N-th scan driving signal is outputted, the clock control is used to perform outputting the (N+1)-th scan driving signal, and so on.
The embedded touch technology is to integrate the touch panel with the liquid crystal (LC) panel, and embed the function of the touch panel to the LC panel so that the LC panel can both display and sense the touch to input. As the display technology rapidly grows, the touch panel is widely accepted and used, such as, smart phone, tablet, and so on.
The current embedded technology can be categorized in two types. The first type is the on-cell type and the other is in-cell type.
In the known technologies, the in-cell type touch display panel realize the sensing of the touch signals in the display duration or the blanking duration. Take the GOA circuit with a plurality of N-type TFT as an example. The operation timing of known driving method for in-cell type display panel is shown in FIG. 1. During displaying a frame, the touch scan signal TP SCAN turns on at the point when the n-th stage GOA unit finishes outputting the scan driver signal G(n), i.e., activating the touch signal sensing. After the touch scan signal TP SCAN turns on, the clock signal CK and the inverted clock signal XCK both are pulled down to the low level.
As shown in FIG. 2, the GOA circuit comprises a plurality of cascade GOA units, each stage GOA unit inputs a clock signal CK, an inverted clock signal XCK, and a constant negative voltage VSS, and outputs a corresponding scan driver signal. FIG. 3 and FIG. 4 shows examples of the GOA circuit of the n-th stage GOA unit respectively. In FIG. 3, the first node Q(n) is first pulled down to the level of the scan driver signal G(n), then pulled down by the scan driver signal G(n) to the level of constant negative voltage VSS. In FIG. 4, the first node Q(N) and the scan driver signal G(n) are both pulled down directly to the level of the constant negative voltage VSS.
Refer to FIG. 1 and FIG. 2. In general, before the touch scan signal TP SCAN is turned on, the high level of the first node of each stage GOA unit maintains at the high level of the first node of the GOA of the previous stage. However, when the touch scan signal TP SCAN is turned on, the first node Q(n) and Q(n+1) of the GOA units of the previous stage and the next stage neighboring the rising edge of the touch scan signal TP SCAN will be dragged, which will cause the first node of the GOA units of the previous stage and the next stage neighboring the rising edge of the touch scan signal TP SCAN to form different voltage waveform. The difference in voltage holding time will cause different extent of electricity leakage, and the TFT having different time under the voltage stress will also cause different extent of ageing in TFT. Therefore, in addition to the abnormal display generated by the scan driver signal difference from the GOA units of the other stages cause by leakage, the TFT ageing in the GOA units of previous and the next stages will also shorten the lifespan of the circuit.